1. 53 The Chemical Senses: Taste and Smell Dr. A.R. Jamshidi Fard 2011

2. Gustation - Taste

3. Taste Buds Most of the 10,000 or so taste buds are found in papillae (projections) of the tongue mucosa Papillae: filiform, fungiform, and circumvallate Fungiform and circumvallate papillae have taste buds Consist of three major cell types: Supporting cells – insulate the receptor Basal cells – divide & differentiate into supporting cells Gustatory cells – taste cells

4. Taste Buds

5. Taste Receptors At least 13 possible or probable chemical receptors in the taste cells: 2 sodium receptors 2 potassium receptors 1 chloride receptor 1 adenosine receptor 1 inosine receptor 2 sweet receptors 2 bitter receptors 1 glutamate receptor 1 hydrogen ion receptor

6. Taste Sensations Five basic taste sensations: Sweet – sugars, alcohols, some amino acids Salty – metal ions (inorganic salts) Sour – hydrogen ions (acids) Bitter – alkaloids such as quinine, caffeine, nicotine Umami – elicited by the amino acid glutamate

7. Physiology of Taste In order to be tasted, a chemical must be dissolved in saliva and contact gustatory cells Binding of the chemical depolarizes the taste cell membrane, releasing neurotransmitter Binding of the neurotransmitter to the sensory dendrites initiates generator potentials that may elicit an action potential

8. Gustatory Pathway Cranial Nerves VII and IX carry impulses from taste buds to the solitary nucleus of the medulla These impulses then travel to the thalamus, and from there fibers branch to the: Gustatory cortex in the parietal lobes Hypothalamus and limbic system (appreciation of taste)

9. Gustatory Pathway

10. Olfaction - Smell

11. Sense of Smell The organ of smell is the olfactory epithelium, which covers the superior nasal concha Olfactory receptor cells are bipolar neurons with radiating olfactory cilia Olfactory receptors are surrounded and cushioned by supporting cells. Basal cells lie at the base of the epithelium Axons of the olfactory receptor cells form Filaments of Cranial nerve I and project superiorly through the cribriform plate to synpase with the olfactory bulbs

12. Sense of Smell

13. Filaments synapse with second-order neurons in the Olfactory bulbs. Impulses leave via the olfactory tracts and follow two pathways. One pathway travels via the thalamus to the olfactory cortex and part of the frontal lobe just above the orbit. The other pathway travels to the hypothalamus, amygdala, and other regions of the limbic system (emotional response) GABA-releasing cells in the olfactory bulb can inhibit some of the second-order neurons, so that only highly excititatory inpulses are transmitted. This contributes to olfactory adaptation.

14. Olfactory Pathway

15. Basic Smells 1. Camphoraceous کافوری 2. Musky مشک دار 3. Floral گلدار 4. Pepperminty نعناعی 5. Ethereal اتری 6. Pungent تند و زننده 7. Putrid فاسد و متعفن

16. Taste Your Life ! As long as You alive !